This invention relates to knotters for use with agricultural baling machines.
In conventional hay balers, crop material is picked up from the ground by a pick-up unit and fed into an elongated bale chamber in timed sequence with a reciprocating plunger. The plunger compresses the material into bales, and at the same time, gradually advances the bales towards the outlet end of the bale chamber. As the bales reach a predetermined length, a knotter is actuated to wrap twine around the bale and secure the ends of the twine together.
In a typical baler, the knotter is mounted on the bale chamber and includes a twine holder from which twine extends to encircle a bale. During the baling operation, a leading strand of twine is held by the twine holder and extends forwardly across a twine retainer finger and a billhook and then in front of the bale. The twine retainer finger supports the leading strand of twine so that it does not bear forcefully against the billhook. A needle is used to complete the encirclement of the twine around the bale and, when advancing, the needle lays a trailing strand across the twine retainer finger, billhook and twine holder. A twine finger captures the leading and trailing strands of twine and positively positions them against the heel of the billhook. The twine strands are then twisted into a bight by the billhook and a portion thereof is partially pulled through the bight to form a bow knot. A knife then cuts the twine from the twine supply so that the tied bale is complete in itself.
An improved knotter disclosed in British application No. 2,081,312, published Feb. 17, 1982, has been found to be highly reliable in operation. However, this improved knotter has a drawback in that it may give rise to knot misties due to the strands of twine entering between the jaws of the billhook prematurely. In the knot-tying operation of this improved knotter, the billhook rotates through a first cycle and a second cycle. The jaws of the billhook are opened in each cycle even though the strands of twine are only required to enter between the jaws during the second cycle. This dual opening of the billhook jaws for each knot-tying operation was not considered to impair the operation of the improved knotter since the opening during the first cycle, albeit unnecessary, should have no adverse effect. During the first cycle of the knot tying operation, the twine is pushed off a guide member and it has been found that sometimes the twine jumps from the guide member into the open jaws of the billhook, thus giving rise to a knot mistie. Such an occurrence is relatively rare but it is very desirable to eliminate all misties and the object of the present invention is to prevent misties due to the premature placement of the twine between the jaws of the billhook.